The present invention relates to an industrial robot and more particularly to that suitable for carrying out assembling and transportation of material in the manufacturing process.
In recent years a growing number of industrial robots are being developed and put into service. Many of these industrial robots have very small work ranges, so that the entire process is divided into a number of smaller work elements, each being assigned to respective industrial robots. This facilitates the control of the robots and improves the tact time.
Since the large number of robots must be installed, the industrial robot is first required to be small in size and light in weight, as well as inexpensive. Further, to reduce the tact time the industrial robot must be able to move at high speed.
One example of a conventional industrial robot is shown in FIG. 1.
This robot has a first arm 201 and a second arm 202 supported horizontally by two joints. At the base of the first arm 201 is provided a DC servomotor 203 to directly drive the first arm 201. A similar DC servomotor 204 is provided to the base of the second arm 202 pivoted at the front end of the first arm 201 so as to directly drive the second arm 202.
Provided at the front end of the second arm 202 is an air cylinder 205. A vertically moving shaft 206 is mounted to the end of the piston rod of the air cylinder 205 with a hand 207 pivotally supported at the lower end of the shaft 206.
The hand 207 is moved up and down by the extension and contraction of the air cylinder 205. A stepping motor 209 is secured to the base 208 to transmit the rotating force to the hand 207 through timing belts 210, 210', 210" and pulleys 211, 211', 211", 211"' to cause the hand 207 to perform twisting actions.
The above robot has a total of four degrees of freedom, i.e., two degrees of freedom in the horizontal plane defined by the first and second arms 201, 202, one degree of freedom in the vertical direction, and one degree of freedom given by the rotation of hand 207. They are used in assembling parts from above.